Use of an SDB is a key design strategy to reduce the circuit area to enable high-density integrated circuits. In current SDB designs, the shallow trench isolation (STI) layer is a standard shape and at the same height with other structure locations. However, since the dummy gate will be on this STI between two fins, the leakage path or weak point will be a source of potential defects. Moreover, with the current T-shaped SDB process flow, one mask is used to generate a higher oxide STI under the SDB and an additional mask and additional oxide deposition/etch process steps are used to form the SDB. The requirement of two masks, or reticles, makes the current process flow costly.
A need therefore exists for methodology enabling formation of a T-shaped SDB using a single-mask process flow.